Display the stdio output in an iframe and reload after completion of re-reun.

The output returned from layout-tests-server can be displayed in an iframe.
After completion of re-run from dashboard.html it has to automatically reload the latest dashboard.

BUG=418580

Review URL: https://codereview.chromium.org/616533002

git-svn-id: svn://svn.chromium.org/blink/trunk@182900 bbb929c8-8fbe-4397-9dbb-9b2b20218538